As has been described in the aforementioned copending application, it is known to provide plastic or synthetic resin tubes which can be bundles and can serve as cable guide bundles enabling cabling, for example, communications or power cabling, to be passed through the tubes which can be placed in the ground.
The tube assemblies can be fabricated and wound on a drum or into a drum shape, can be transported in this state and, for forming the tube bundle, can be fed off the drum or out of the coil condition and then assembled so that the compact configuration of the assembly of tubes is formed, i.e. the tubes are fastened together into a tube bundle.
To affix the tubes in the tube bundle, strapping can be provided around the tubes or the tubes can be formed with connecting elements at their outer tubes of the array which can interfit or interlock. The configuration and attachments are such that the tube bundle can be laid either straight or in an arcuate configuration.
The material from which the tube assembly is formed should be sufficiently elastically deformable to allow the described coiling and uncoiling, the assembly of the tubes into the tube bundle and the detachment of interfitting parts or attachment thereof as described. For example, the tubes may be composed of polyethylene or polyvinylchloride. The tube assembly can be made by techniques known in the tube and pipe extrusion arts for the extrusion of plastic pipes and tubes.
Tube bundles for cabling have been provided in various configurations heretofore and by and large the tubes of the tube bundles have been composed of individual plastic tubes of round, usually circular cross section. This configuration simplifies fabrication and ensures the coiling and uncoiling of the assembly without problems.
However the individual plastic tubes in the cabling tube bundle do not fit together or define complementary structures in which other tubes can nest in a fully satisfactory manner. It is not possible, for example, with such constructions to provide highly compact and stable tube bundles capable of withstanding compression and like forces which may be severe in below ground uses. It is not possible, for example, to interfit the tubes so that square or rectangular parts thereof nest together in surface contact or engage in a nested manner like hexagonal structures of a beehive. As a consequence, in the prior art structures substantial gaps or interstices are formed between the individual cable-receiving tubes. If the tube bundle is not protected by an outer tube or sheath and is utilized for direct in-ground applications, shocks, pressures and the like can open gaps between the exterior and these interstices of the tube bundle into which water can pass and cause problems. For example, the interstices or spaces between the tubes can then form channels which can carry water into cable shafts or the like to which the cabling assemblies extend or from which the cabling assemblies leave.
It has been proposed to form a tube bundle from a multiplicity of plastic tubes which have modified triangular cross sections such that the vertices of these cross sections, corresponding to the edges defined between sides of the tube are greatly rounded While such tubes allow surface contact between the sides in a manner which cannot be duplicated with circular outer cross section tubes, nevertheless substantial free space is provided by reason for the considerable rounding of the triangle corners. These free spaces effectively become dead spaces, since cables cannot be fed through them as a practical manner. Furthermore, experience has shown that the engagement of groups of such tubes along their surfaces and the use of a triangular configuration so rigidifies the assembly that an assembly of such tubes cannot be wound or unwound readily, thereby creating difficulty in the usual handling of plastic tube assemblies for direct in-ground cabling purposes.